From d375278d666760e195693b57415ba0a125cadd55 Mon Sep 17 00:00:00 2001 From: H Hartley Sweeten Date: Fri, 8 Apr 2016 10:14:58 -0700 Subject: [PATCH] staging: comedi: das1800: fix possible NULL dereference DMA is optional with this driver. If it was not enabled the devpriv->dma pointer will be NULL. Fix the possible NULL pointer dereference when trying to disable the DMA channels in das1800_ai_cancel() and tidy up the comments to fix the checkpatch.pl issues: WARNING: line over 80 characters It's probably harmless in das1800_ai_setup_dma() because the 'desc' pointer will not be used if DMA is disabled but fix it there also. Fixes: 99dfc3357e98 ("staging: comedi: das1800: remove depends on ISA_DMA_API limitation") Cc: # 4.0+ Signed-off-by: H Hartley Sweeten Reviewed-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/das1800.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/drivers/staging/comedi/drivers/das1800.c b/drivers/staging/comedi/drivers/das1800.c index 940781183fac..3be10963f98b 100644 --- a/drivers/staging/comedi/drivers/das1800.c +++ b/drivers/staging/comedi/drivers/das1800.c @@ -567,14 +567,17 @@ static int das1800_cancel(struct comedi_device *dev, struct comedi_subdevice *s) struct comedi_isadma_desc *desc; int i; - outb(0x0, dev->iobase + DAS1800_STATUS); /* disable conversions */ - outb(0x0, dev->iobase + DAS1800_CONTROL_B); /* disable interrupts and dma */ - outb(0x0, dev->iobase + DAS1800_CONTROL_A); /* disable and clear fifo and stop triggering */ - - for (i = 0; i < 2; i++) { - desc = &dma->desc[i]; - if (desc->chan) - comedi_isadma_disable(desc->chan); + /* disable and stop conversions */ + outb(0x0, dev->iobase + DAS1800_STATUS); + outb(0x0, dev->iobase + DAS1800_CONTROL_B); + outb(0x0, dev->iobase + DAS1800_CONTROL_A); + + if (dma) { + for (i = 0; i < 2; i++) { + desc = &dma->desc[i]; + if (desc->chan) + comedi_isadma_disable(desc->chan); + } } return 0; @@ -934,13 +937,14 @@ static void das1800_ai_setup_dma(struct comedi_device *dev, { struct das1800_private *devpriv = dev->private; struct comedi_isadma *dma = devpriv->dma; - struct comedi_isadma_desc *desc = &dma->desc[0]; + struct comedi_isadma_desc *desc; unsigned int bytes; if ((devpriv->irq_dma_bits & DMA_ENABLED) == 0) return; dma->cur_dma = 0; + desc = &dma->desc[0]; /* determine a dma transfer size to fill buffer in 0.3 sec */ bytes = das1800_ai_transfer_size(dev, s, desc->maxsize, 300000000); -- 2.34.1